WHY you should not add GRAVELS to Pots: Busting an Old Myth

After reading this post, you’ll never put gravel or other coarse materials at the bottom of pots. Must find out, WHY?

Every time you prepare a pot for planting you add a layer of gravel in the bottom for drainage! But, is it really necessary or not required at all?

Adding a layer of gravel, stones or pot shards in the bottom of the container is a common practice that most of the gardeners (old or new or even experts) do. But do you really need to do this? We say NO!

We have grown plants in containers successfully without adding gravels to pots, and there seems no problem with it. Our plants have done really fine and never suffered from root rot or drainage problem. Let’s find out why it is NOT NECESSARY TO ADD GRAVELS or other coarse materials IN POTS!

WE CALL IT ABSOLUTELY A MYTH THAT IF YOU DON’T ADD GRAVELS IN THE BOTTOM OF THE POT THERE WILL BE A DRAINAGE PROBLEM AND YOUR PLANTS WILL DIE DUE TO WATERLOGGING; ALBEIT, THE OPPOSITE IS TRUE!

To support our claim, we refer to this educative article on Illinois University, according to them “It is a myth that a layer of gravel (inside the bottom of an individual pot) beneath the soil improves container drainage. Instead of extra water draining immediately into the gravel, the water ‘perches’ or gathers in the soil just above the gravel. The water gathers until no air space is left. Once all the available soil air space fills up, the excess water drains into the gravel below. So gravel in the bottom does little to keep soil above it from being saturated by overwatering.“

Gravel Improves Drainage?

Adding a drainage layer looks like an important custom, and it seems a plausible chore. Many gardening experts, even some gardening show hosts, and experienced gardeners suggest this, BUT the soil SCIENTISTS have proved that adding gravel or other coarse material instead of improving drainage impairs it. The soil scientist Kevin Handreck, the author of Gardening Down-Under and Good Gardens with Less Water, even believe that crocking increases the risk of damaging your plants by overwatering.

The Associate Professor Linda Chalker-Scott, an urban horticulturist at Washington State University, calls it a myth that refuses to die. In her report, she also questions gardening websites and books– “Regardless of solid scientific evidence to the contrary! Nearly every book or website on container gardening recommends placing coarse material at the bottom of containers for drainage.“ Read her article on Sustainable Gardening here!

A Layer of Gravel Improves Air Circulation?

We know that plants need good drainage so that their roots can receive adequate oxygen, and we also know that water passes through a coarsely textured material faster than it does in fine material. But what we miss here is that water does not move easily from layers of finer textured materials to layers of more coarse-textured materials, which means instead of passing freely and easily the water sits between the soil and drainage layer and doesn’t start to drip until the soil is saturated completely. ABC SCIENCE also tried to debunk this myth in its article, click here!

Let’s understand this with sponge test:

Julie Day posted a similar article on Today’s Homeowner in which she equated soil with a sponge and wrote– “Water won’t run out into the gravel, or out of the pot, or anywhere until the soil is saturated. If you don’t believe me, try laying a sponge on top of a pile of gravel, then pour water into the sponge. Does the gravel make the sponge drain faster? No, the sponge fills up, and it won’t drip until it can’t hold another drop.“ Read the complete article here!

Bottom Layer Worsen the Drainage?

In our practice, we didn’t find any help from adding a bottom layer of coarse material in containers. The BBC.com too posted an article on this with the title “Are gardeners wrong to put ‘crocks’ in plant pots?“, Several years ago– “You might think that the bigger gaps where soil meets bits of broken crockery would allow more water to filter through. But this turns out not to be the case, some argue. Guy Barter, the chief horticultural adviser at the RHS, says a crock is actually likely to worsen drainage by creating a block.“

Gravel Takes the Space

Already, space is so limited as you’re cramming a plant in a container and then you add a few inches of gravels or crockery for drainage, what it does is reduces the volume of soil available to plant roots, reported The Guardian in their article Old Wives’ Tales. Basically, it means you make a pot even smaller in size and as a result get an unhappy crowded plant.

The article by James D. Kramer on the website Fine Gardening also support our claim “While it’s a common practice to put gravel or charcoal in the bottom of pots, they don’t help with drainage and take up valuable space, so I don’t recommend using them.” Check out this interesting article here!

Adding a Drainage Layer in the Bottom Causes Root Rot

University of California’s Master Gardener, Sue McDavid write this– “Plants like good drainage, especially those in containers. If water pools around plant roots too long, root rot will damage and possibly even kill the plant. For too long, gardeners have been covering the bottom of containers with gravel, pieces of broken pottery, Styrofoam packing material and the like. Do not do this… only the potting mix should be put into a plant container. Instead of water draining immediately through the soil, then into gravel or other material and on out the drainage holes, water will completely saturate the soil so that no air spaces are left. This could take a long time, and in the interim, plant roots will be starved for oxygen.” See the full in the PDF here!

Gravel Adds Unnecessary Weight

This is one more reason to avoid this– A layer of gravel or pots shards or anything at the bottom of a pot adds unnecessary weight to a container because it is heavier than most lightweight potting soils and it becomes hard to move.

The Gardenweb forum has a very interesting discussion between gardeners on adding coarse materials at the bottom of pots, must see that too. Here is the link!

What Should You Do?

Nothing, as Master Gardener Sue McDavid said– Only the potting mix should be put into a plant container, there is no need of a drainage layer, and you can skip it. However, if you fear of the soil to wash out (which is not going to happen either), you can prevent soil from this by placing a layer of paper towel or newspaper over the holes before adding mix. Also, ensure that you never grow plants in a pot without drainage holes and always check at the bottom to see whether there are sufficient holes or not before planting.

12 COMMENTS

Totally agree……I always use an Onion bag mesh cut to the size of the bottom of pot……to stop mix from washing out ofthe pot…..i use quite big drainage holes for my citrus trees in pots and use onion mesh with every pot…..its very effective at preventing mix from draining away.

I agree with this article, however, I do put a layer of gravel in the bottom of my pots in order to weight them so the high winds in our area don’t knock them over. I lost a lot of nice ceramic and terra cotta pots in the past due to the winds lifting them and tossing them around the yard! The rock weight really helped prevent that. It’s good to know how it impacts the soil and root systems, though. I’ll have to be careful to watch the plants more closely and avoid overwatering. Thanks for sharing!

I don’t agree I ‘ve used white marble rocks which I buy at Ace hardware . I always rinse it before I place them in the pots. Never had a problem . I also used the rocks in the pots for my indoor house plants. All my plants grow beautifully!!!

What about using a layer of perlite at the bottom of the pot? Probably the same effect as gravel? Wish I’d known this sooner. I think my snake plant is suffering from not enough nutrient-rich soil and not enough room for its roots…

Succulent web sites recommend covering the pot hole with a piece of screen, like the mesh made for patching wall board. It sticks in place and then gets covered with lava rock and/or activated carbon. This is supposed to allow the drainage that succulents need. I have started to sue lava rock with other plants too but it is too soon to know the effect because I repotted some annuals that I brought in before frost. Years ago, I read about putting a layer of window screen in the bottom of the pot to keep the soil from washing out the drainage holes and that seems to work too.